Automated material handling system for semiconductor manufacturing based on a combination of vertical carousels and overhead hoists

ABSTRACT

A highly efficient Automated Material Handling System (AMHS) that allows an overhead hoist transport vehicle to load and unload Work-In-Process (WIP) parts directly to/from one or more WIP storage units included in the system. The AMHS includes an overhead hoist transport subsystem and at least one vertical carousel stocker having a plurality of storage bins. The overhead hoist transport subsystem includes an overhead hoist transport vehicle traveling along a suspended track defining a predetermined route, which runs adjacent to the carousel stocker, thereby allowing the overhead hoist transport vehicle to access a WIP part directly from one of the storage bins. At least one of the storage bins includes a movable shelf operative to move laterally from a first position along the carousel path to a second position near the overhead hoist transport vehicle.

CLAIM OF PRIORITY

This application is a continuation of and claims priority under 35U.S.C. §120 to U.S. application Ser. No. 14/080,590 filed Nov. 14, 2013,which is a divisional of an claims priority to U.S. application Ser. No.13/492,341 filed Jun. 8, 2012, which is a continuation of and claimspriority under 35 U.S.C. §120 to U.S. patent application Ser. No.12/724,194, filed Mar. 15, 2010, which issued as U.S. Pat. No. 8,197,172and is entitled “AUTOMATED MATERIAL HANDLING SYSTEM FOR SEMICONDUCTORMANUFACTURING BASED ON A COMBINATION OF VERTICAL CAROUSELS AND OVERHEADHOISTS, which is a continuation of and claims priority under 35 U.S.C.§120 to U.S. patent application Ser. No. 11/652,707, filed Jan. 12,2007, which issued as U.S. Pat. No. 7,771,153 and is entitled “AUTOMATEDMATERIAL HANDLING SYSTEM FOR SEMICONDUCTOR MANUFACTURING BASED ON ACOMBINATION OF VERTICAL CAROUSELS AND OVERHEAD HOISTS,” which is acontinuation of and claims priority under 35 U.S.C. §120 to U.S. patentapplication Ser. No. 10/393,526, filed Mar. 20, 2003, which issued asU.S. Pat. No. 7,165,927 and is entitled “AUTOMATED MATERIAL HANDLINGSYSTEM FOR SEMICONDUCTOR MANUFACTURING BASED ON A COMBINATION OFVERTICAL CAROUSELS AND OVERHEAD HOISTS,” which claims priority under 35U.S.C. §119(e) to U.S. Provisional Patent Application No. 60/389,993,filed Jun. 19, 2002 and entitled “AUTOMATED MATERIAL HANDLING SYSTEM FORSEMICONDUCTOR MANUFACTURING BASED ON A COMBINATION OF VERTICAL CAROUSELSAND OVERHEAD HOISTS,” and U.S. Provisional Patent Application No.60/417,993, filed Oct. 11, 2002 and entitled “OFFSET ZERO FOOTPRINTSTORAGE (ZFS) USING MOVING SHELVES OR A TRANSLATING HOIST PLATFORM,” theentire contents of each of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates generally to automated material handlingsystems, and more specifically to an automated material handling systemthat allows an overhead hoist to access work-in-process (WIP) partsdirectly from a WIP storage unit to increase the efficiency of theoverall material handling system.

Automated material handling systems are known that employ WIP storageunits and overhead hoists to store and transport WIP parts betweenvarious workstations and/or processing machines in a productmanufacturing environment. For example, such an Automated MaterialHandling System (AMHS) is commonly employed in the manufacturing ofIntegrated Circuit (IC) chips. A typical process for fabricating an ICchip comprises various steps including deposition, cleaning, ionimplantation, etching, and passivation steps. Further, each of thesesteps in the IC chip fabrication process is usually performed by adifferent processing machine such as a chemical vapor depositionchamber, an ion implantation chamber, or an etcher. Accordingly, the WIPparts, e.g., semiconductor wafers, are typically transported between thedifferent workstations and/or processing machines multiple times toperform the various process steps required for fabricating the IC chips.

A conventional AMHS for manufacturing IC chips comprises a plurality ofWIP storage units (also known as “stockers”) for storing thesemiconductor wafers, and one or more overhead hoist transport vehiclesfor transporting the wafers between the various workstations andprocessing machines on the IC chip manufacturing floor. Thesemiconductor wafers stored in the WIP stockers are typically loadedinto cassette pods such as Front Opening Unified Pods (FOUPs), which aresubsequently transferred to an overhead transport vehicle configured totravel on a suspended track. In the conventional AMHS, each stocker istypically provided with a plurality of active input/output ports thatwork in conjunction with an internal robotic arm (which may provide upto three or more axes of movement) for loading and unloading the FOUPsto/from the stocker. The FOUPs are picked and placed from/to theinput/output ports by the overhead hoist vehicle.

One drawback of the conventional AMHS is that the efficiency of theoverall system is limited by the time required for the robotic arm toaccess the FOUPs at the WIP stocker's active input/output ports. Becauseof the generally delicate nature of the semiconductor wafers, strictlimits are normally imposed on the acceleration rate of the robotic arm.For this reason, a minimum amount of time is typically required formoving the FOUPs to and from the stocker's input/output ports. Thisminimum move time generally determines the stocker throughput, whichdictates the number of stockers needed to support the desired IC chipproduction level and thus the total cost of the AMHS. Although thematerial handling efficiency of the AMHS might be improved by increasingthe number of active input/output ports on each stocker and by allowingthe overhead transport vehicle to access multiple input/output portssimultaneously, providing additional input/output ports cansignificantly increase the cost of the stocker.

In addition, the combination of a three or more axis internal robot inthe stocker with several input/output ports, each having 1-3 axes ofmotion, means that a typical stocker may have between 5 and 16 axes ofmotion. This is a very complex, low reliability, and costly solution forstoring material.

It would therefore be desirable to have an automated material handlingsystem that provides enhanced material handling efficiency whileovercoming the drawbacks of conventional automated material handlingsystems.

BRIEF SUMMARY OF THE INVENTION

In accordance with the present invention, a highly efficient AutomatedMaterial Handling System (AMHS) is provided that allows an overheadhoist to load and unload Work-In-Process (WIP) parts directly to/fromone or more WIP storage units included in the system.

In one embodiment, the improved AMHS comprises an overhead hoisttransport subsystem and at least one vertical carousel WIP storage unit(“stocker”) including a plurality of storage bins. The overhead hoisttransport subsystem includes at least one overhead hoist transportvehicle configured to travel along a suspended track defining at leastone predetermined route. The predetermined route passes over thevertical carousel stocker, which is configured to allow the overheadhoist to access one or more WIP parts directly from a selected one ofthe carousel storage bins. In this first embodiment, the selectedcarousel storage bin containing the desired WIP lot(s) is positioned atthe top of the vertical carousel stocker substantially directlyunderneath the suspended track. Next, the overhead hoist transportvehicle is moved along the suspended track to a position substantiallydirectly above the selected carousel storage bin. The overhead hoist isthen lowered toward the selected storage bin. Finally, the overheadhoist is operated to pick the desired WIP lot directly from the carouselstorage bin, or to place one or more WIP lots in the carousel storagebin.

In a second embodiment, the predetermined route defined by the suspendedtrack passes parallel to the vertical carousel WIP stocker, which isconfigured to allow the overhead hoist to access one or more WIP partsdirectly from one of the carousel storage bins. The AMHS furtherincludes an extraction mechanism, which works in conjunction with thevertical carousel stocker to suitably position the selected carouselstorage bin containing the desired WIP lot(s) relative to the track. Forexample, the extraction mechanism may be configured to move the selectedcarousel storage bin (e.g., a movable shelf) along a singleservo-controlled axis from a first position adjacent the track to asecond position substantially directly underneath the track. In thesecond embodiment, the overhead transport vehicle is moved along thetrack to a position substantially directly above the second position.Next, the overhead hoist is lowered toward the second position. In analternative embodiment, the selected carousel storage bin comprises ashelf positioned alongside the track, and the overhead hoist is mountedto a translating stage for picking and placing one or more WIP lots tothe shelf at the side of the overhead transport vehicle. Finally, theoverhead hoist is operated to pick the desired WIP lot directly from theselected storage bin, or to place one or more WIP lots in the selectedstorage bin.

By configuring the AMHS to allow the overhead hoist to directly load andunload WIP parts to/from the carousel storage bins from a position abovethe respective storage bin, more efficient AMHS operation can beachieved.

Other features, functions, and aspects of the invention will be evidentfrom the Detailed Description of the Invention that follows.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The invention will be more fully understood with reference to thefollowing Detailed Description of the Invention in conjunction with thedrawings of which:

FIG. 1 is a perspective view of a conventional automated materialhandling system;

FIG. 2 is block diagram of a first embodiment of an automated materialhandling system according to the present invention;

FIG. 3 is a block diagram of a second embodiment of the automatedmaterial handling system of FIG. 2;

FIG. 4 is a block diagram of a third embodiment of the automatedmaterial handling system of FIG. 2;

FIGS. 5a-5b are block diagrams of a translating hoist vehicle accessingfixed storage positions according to the present invention;

FIG. 6 is a block diagram of the translating hoist vehicle of FIGS.5a-5b accessing material on a conveyer; and

FIG. 7 is a flow diagram of a method of operating the automated materialhandling system of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

The entire disclosures of U.S. patent application Ser. No. 10/393,526filed Mar. 20, 2003 entitled AUTOMATED MATERIAL HANDLING SYSTEM FORSEMICONDUCTOR MANUFACTURING BASED ON A COMBINATION OF VERTICAL CAROUSELSAND OVERHEAD HOISTS, U.S. Provisional Patent Application No. 60/389,993filed Jun. 19, 2002 entitled AUTOMATED MATERIAL HANDLING SYSTEM FORSEMICONDUCTOR MANUFACTURING BASED ON A COMBINATION OF VERTICAL CAROUSELSAND OVERHEAD HOISTS, and U.S. Provisional Patent Application No.60/417,993 filed Oct. 11, 2002 entitled OFFSET ZERO FOOTPRINT STORAGE(ZFS) USING MOVING SHELVES OR A TRANSLATING HOIST PLATFORM, areincorporated herein by reference.

An Automated Material Handling System (AMHS) is disclosed that can loadand unload Work-In-Process (WIP) parts to/from a WIP storage unit withincreased efficiency. The presently disclosed AMHS achieves suchincreased material handling efficiency by allowing top-loading/unloadingof storage bins in a vertical carousel WIP storage unit by an overheadhoist positioned above the respective storage bin.

FIG. 1 depicts a conventional AMHS 100, which may be employed toautomatically store and transport WIP parts between various workstationsand/or processing machines in a product manufacturing environment, e.g.,a clean environment for manufacturing Integrated Circuit (IC) chips. Asshown in FIG. 1, the conventional AMHS 100 comprises a WIP storage unit(“stocker”) 102 and an overhead hoist transport subsystem 104. The WIPstocker 102 includes input and output ports 111-112, and the overheadhoist transport subsystem 104 includes a suspended track 108 and aplurality of overhead hoist transport vehicles 105-106 configured totravel on the track 108. In a typical mode of operation, the WIP partsare transported in a cassette pod 110 such as a Front Opening UnifiedPod (FOUP). The first overhead transport vehicle 105 travels along thetrack 108 and stops at a position suitable for unloading the FOUP 110into the input port 111 or for loading another FOUP from the output port112 of the stocker 102. Further, the second overhead transport vehicle106 waits on the track 108 until the first overhead transport vehicle105 finishes unloading/loading the FOUP and moves out of the way.

In the conventional AMHS 100, FOUPs are unloaded from the overhead hoistinto the input port 111, loaded from the output port 112 into theoverhead hoist, or otherwise accessed from within the stocker 102 by arobotic arm 107, which may provide up to three or more axes of movement.Further, the minimum amount of time required to access the FOUPs fromthe stocker 102 generally determines the stocker throughput, whichdictates the number of stockers needed to support the desired productionlevel. Accordingly, complex movements of the multi-axis robotic arm 107for accessing the FOUPs may cause the minimum move time to increase,thereby increasing both the number of stockers needed in the AMHS 100and the overall cost of the material handling system.

FIG. 2 depicts an illustrative embodiment of an Automated MaterialHandling System (AMHS) 200, in accordance with the present invention. Inthe illustrated embodiment, the AMHS 200 comprises an overhead hoisttransport subsystem 204, and at least one vertical carousel WIP storageunit (“stocker”) 202 including a plurality of storage bins such as acarousel storage bin 203. The vertical carousel WIP stocker 202 isconfigured to allow an overhead hoist in the overhead hoist transportsubsystem 204 to access WIP parts directly from a selected one of thecarousel storage bins.

It is noted that like the conventional AMHS 100 (see FIG. 1), the AMHS200 of FIG. 2 may be employed in a clean environment for manufacturingIC chips such as a 200 mm or 300 mm FAB plant, or any other suitableproduct manufacturing environment. As shown in FIG. 2, the IC chipmanufacturing environment includes first and second floors 220 and 226,and a ceiling 214. The first floor 220 typically comprises a waffle slabmade of reinforced concrete, and the second floor 226 comprises a raisedfloor located above the waffle slab 220. The vertical carousel stocker202 is positioned on the waffle slab 220. Further, workstations and/orprocessing machines (not shown) configured to perform various processsteps for fabricating the IC chips are positioned on the raised floor226, which is typically covered with an electrically nonconductivematerial and designed to meet specific loading and seismic requirements.For example, the raised floor 226 may be located a distance 228 (about0.6 m) above the waffle slab 220 and a distance 224 (greater than orequal to about 4.15 m) below the ceiling 214.

In the presently disclosed embodiment, the vertical carousel stocker 202includes a housing 252, and first and second pulleys 250-251 and a belt254 disposed within the housing 252. As shown in FIG. 2, the carouselstorage bins (e.g., the storage bin 203) are coupled to the belt 254 atvarious spaced locations along the belt, and the belt 254 is loopedbetween the first and second pulleys 250-251 to allow the storage binsto be rotatably positioned along the belt path by driving one of thepulleys 250-251. For example, the vertical carousel stocker 202 may havea height 218 (about 3.85 m). The top of the vertical carousel stocker202 may therefore be a distance 216 (about 3.25 m) above the raisedfloor 226.

As described above, the vertical carousel stocker 202 is configured toallow an overhead hoist to access WIP parts, e.g., semiconductor wafers,directly from one of the carousel storage bins. In the illustratedembodiment, the portion of the stocker housing 252 near the ceiling 214is at least partially open to allow top-loading/unloading of theselected carousel storage bin. Further, each carousel storage bincomprises a fixed shelf, and the semiconductor wafers are loaded intocassette pods such as a Front Opening Unified Pod (FOUP) 210 disposed onthe shelf 203. For example, each FOUP 210 may hold one or moresemiconductor wafer lots, thereby allowing the overhead hoist to accessmultiple wafer lots in a single carousel storage bin simultaneously.

The overhead hoist transport subsystem 204 includes a suspended track208 and at least one overhead hoist transport vehicle 205 configured fortraveling on the track 208. The suspended track 208 defines at least onepredetermined route passing over the vertical carousel stocker 202,thereby allowing the overhead transport vehicle 205 to access a FOUPdirectly from one of the carousel storage bins positioned approximatelyat the top of the stocker 202. For example, the overhead transportvehicle 205 may extend a distance 222 (about 0.9 m) from the ceiling214.

In an illustrative mode of operation, the selected carousel storage bin,e.g., the storage bin 203 containing the FOUP 210, is positionedapproximately at the top of the vertical carousel stocker 202 underneaththe track 208. The overhead transport vehicle 205 is then moved alongthe track 208 to a position substantially directly above the storage bin203. Next, the overhead hoist is lowered from the overhead transportvehicle 205 through the opening in the stocker housing 252 toward thestorage bin 203. For example, the overhead hoist may be lowered in adirection parallel to the longitudinal axis L₁ of the stocker. Theoverhead hoist is then operated to pick the FOUP 210 directly from thestorage bin 203 for subsequent transport to a workstation or processingmachine on the IC chip manufacturing floor. It is understood that theoverhead hoist may alternatively be operated to place a FOUP in thecarousel storage bin 203.

FIG. 3 depicts an alternative embodiment 300 of the AMHS 200 (see FIG.2). As shown in FIG. 3, the AMHS 300 comprises an overhead hoisttransport system 304, and at least one vertical carousel WIP stocker 302including a plurality of storage bins such as a slide-mounted storagebin 332. Like the vertical carousel stocker 202, the vertical carouselstocker 302 is configured to allow an overhead hoist in the overheadhoist transport system 304 to access WIP parts, e.g., semiconductorwafers, directly from a selected one of the carousel storage bins.

Specifically, the AMHS 300 may be employed in an IC chip manufacturingenvironment including a ceiling 314, a waffle slab 320, and a raisedfloor 326 located above the waffle slab 320. As shown in FIG. 3, thevertical carousel stocker 302 is positioned on the waffle slab 320. Forexample, the raised floor 326 may be located a distance 328 (about 0.6m) above the waffle slab 320 and a distance 324 (greater than about 5.4m) below the ceiling 314. Further, the vertical carousel stocker 302includes a housing 352, and first and second pulleys 350-351 and a belt354 disposed within the housing 352. The carousel storage bins (e.g.,the slide-mounted storage bin 332) are coupleable to the belt 354 atvarious spaced locations along the belt, and the belt 354 is loopedbetween the first and second pulleys 350-351 to allow the storage binsto be rotatably positioned along the belt path by driving one of thepulleys 350-351. For example, the vertical carousel stocker 302 may havea height 318 (about 6 m).

As described above, the vertical carousel stocker 302 is configured toallow an overhead hoist to access the semiconductor wafers directly fromone of the carousel storage bins. In the illustrated embodiment, atleast one side of the housing 352 is at least partially open to allowthe selected carousel storage bin to be extracted from within thehousing 352, and to allow subsequent top-loading/unloading of theselected storage bin by the overhead hoist. Specifically, the AMHS 300further includes at least one extraction mechanism 330, which works toextract the semiconductor wafers from within the stocker 302, and tosuitably position the material relative to a suspended track 308included in the overhead hoist transport subsystem 304. It is noted thateach storage bin may comprise either a movable or fixed shelf. Further,the semiconductor wafers are loaded into cassette pods such as a FOUP310 disposed on the shelf 332.

The overhead hoist transport subsystem 304 includes the suspended track308 and at least one overhead hoist transport vehicle 305 configured totravel on the track 308. The track 308 defines at least onepredetermined route passing parallel to the vertical carousel stocker302, thereby allowing the overhead transport vehicle 305 to access aFOUP directly from a selected one of the slide-mounted storage bins.

In an illustrative mode of operation, the selected slide-mounted storagebin, e.g., the storage bin 332 containing the FOUP 310, is positioned toallow the extraction mechanism 330 to extract the storage bin 332 fromwithin the stocker 302 and to position the storage bin 332 directlyunderneath the track 308. It is noted that the extraction mechanism 330may be incorporated into the stocker 302 and configured to move thestorage bin 332 along a single servo-controlled axis 398. The overheadtransport vehicle 305 is then moved along the track 308 to a positiondirectly above the extracted storage bin 332. Next, the overhead hoistis lowered from the overhead transport vehicle 305 toward the storagebin 332, e.g., in a direction parallel to the longitudinal axis L₂ ofthe stocker. The overhead hoist is then operated to pick the FOUP 310directly from the storage bin 332 for subsequent transport to aworkstation or processing machine on the IC chip manufacturing floor. Itis appreciated that the overhead hoist may alternatively be operated toplace a FOUP in the carousel storage bin 332.

FIG. 4 depicts a detailed embodiment 400 of the AMHS 300 (see FIG. 3).In the illustrated embodiment, the AMHS 400 comprises an overhead hoisttransport system 404 and a vertical carousel stocker 402. The overheadhoist transport system 404 includes a suspended track 408 and anoverhead hoist transport vehicle 405 configured for traveling on thetrack 408. For example, the overhead transport vehicle 405 may extend adistance 436 (about 0.9 m) from the track 408. The vertical carouselstocker 402 includes a plurality of carousel storage bins such as astorage bin 432 disposed within the stocker housing. For example, thestorage bin 432 may be a distance 438 (about 2.6 m) above the raised ICchip manufacturing floor.

As described above, a FOUP 410 is extracted from within the stockerhousing to allow subsequent top-loading/unloading of the selectedstorage bin. The overhead transport vehicle 405 further includes anoverhead hoist 431 having a gripper configured to top-load/unload theFOUP 410 to/from the storage bin 432. In the preferred embodiment, thehoist gripper 430 is mounted on a translating stage to allow theoverhead hoist to pick/place a cassette pod to either side of theoverhead transport vehicle 405.

FIGS. 5a-5b depict a translating hoist vehicle subsystem 704 accessingfixed storage positions. In the illustrated embodiment, the translatinghoist vehicle subsystem 704 includes a suspended track 708, and anoverhead hoist transport vehicle 705 configured to travel on the track.The overhead transport vehicle 705 is configured to pick/place a FOUP710 to a fixed storage position 732. For example, the overhead transportvehicle 705 may extend a distance 736 (about 0.9 m) below the ceiling714, and the storage position 732 may be disposed a distance 738 (about2.6 m) above the raised IC chip manufacturing floor. Further, theceiling 714 may be a distance 790 (about 3.66 m) above the raised floor.

The overhead transport vehicle 705 is configured to pick (and place) theFOUP 710 to a position located directly below the suspended track 708.To that end, the overhead hoist vehicle 705 includes a hoist gripper 731mounted to a translating stage and configured to extend from the vehicle705, pick up the FOUP 710, and retract back to the vehicle 705, therebymoving the FOUP 710 within the overhead transport vehicle 705 (see FIG.5b ). In the preferred embodiment, the translating stage is configuredto allow the overhead hoist to pick/place a cassette pod to either sideof the overhead transport vehicle 705. Once the FOUP 710 is held by thehoist gripper 730, the overhead transport vehicle 705 transports it to aworkstation or processing machine on the IC chip manufacturing floor.

FIG. 6 depicts a translating hoist vehicle system 800 accessing materialeither stored or moving on a conveyer 895. Specifically, an overheadhoist transport subsystem 804 is employed to directly pick or place aFOUP 810 to the overhead rail-based conveyer 895. In the illustratedembodiment, the overhead hoist transport subsystem 804 includes asuspended track 808 and an overhead hoist transport vehicle 805configured to travel on the track 808. For example, the overheadtransport vehicle 805 may extend a distance 836 (about 0.9 m) below thetrack 808 and be disposed a distance 892 (about 0.35 m) above therail-based conveyer 895. Further, the overhead rail 898 may be adistance 838 (about 2.6 m) above the raised IC manufacturing floor. Itshould be understood that the rail 898 extends in a directionperpendicular to the plane of the drawing. The translating hoist vehiclesystem 800 further includes a process tool load port 899.

The overhead transport vehicle 805 may be employed to performtop-loading/unloading of the rail-based conveyer 895. To that end, theoverhead transport vehicle 805 includes an overhead hoist 831 having ahoist gripper 835, which is mounted to a translating stage 833configured to allow both horizontal and vertical motion, as indicated bythe directional arrows 870 and 871, respectively. In an illustrativemode of operation, the rail-based conveyer 895 is moved so that the FOUP810 is positioned directly underneath the overhead hoist 831. The hoistgripper 835 is then lowered via the translating stage 833 toward theFOUP 810, and operated to pick the FOUP 810 directly from the conveyer895. Next, the hoist gripper 835 carrying the FOUP 810 is raised andretracted via the translating stage 833, thereby moving the FOUP 810within the overhead transport vehicle 805. The transport vehicle 805then transports the FOUP 810 to a workstation or processing machine onthe IC chip manufacturing floor.

A method of operating the presently disclosed automated materialhandling system is illustrated by reference to FIG. 7. As depicted instep 902, a selected storage bin containing a FOUP is positioned withina vertical carousel stocker to allow access by an overhead hoist. Forexample, the selected carousel storage bin may be positioned at the topor at the side of the vertical carousel stocker (see FIGS. 2-3). Next,the overhead hoist transport vehicle is moved along a track, as depictedin step 904, to a position adjacent the selected storage bin. In theevent the selected storage bin is positioned at the top of the stocker,the overhead transport vehicle is positioned above the storage bin. Inthe event the selected storage bin is positioned at the side of thestocker, the overhead transport vehicle is positioned to the side of thestorage bin. The overhead hoist is then extended from the transportvehicle and lowered, as depicted in step 906, to allow the hoist gripperto contact the FOUP in the selected storage bin. Next, the hoist gripperis operated, as depicted in step 908, to pick the FOUP directly from thestorage bin. The overhead hoist is then raised and retracted, asdepicted in step 910, to move the FOUP within the overhead transportvehicle. In this way, the FOUP is top-loaded from the selected storagebin to the overhead transport vehicle. Finally, the overhead transportvehicle transports, as depicted in step 912, the FOUP to a workstationor processing machine on the product manufacturing floor.

It will further be appreciated by those of ordinary skill in the artthat modifications to and variations of the above-described automatedmaterial handling system may be made without departing from theinventive concepts disclosed herein. Accordingly, the invention shouldnot be viewed as limited except as by the scope and spirit of theappended claims.

What is claimed is:
 1. A method, comprising: moving a moveable stage of an overhead hoist transport vehicle along a horizontal axis from a first position beneath an overhead rail to a second position adjacent to a side of the OHT vehicle; and moving, by a hoist coupled to the moveable stage, a gripper along a vertical axis to a position that is directly below the moveable stage, wherein the gripper is configured to hold a material unit; obtaining, by a gripper of the overhead transport (OTH) vehicle, the material unit from a suspended shelf; moving, by the overhead transport vehicle, the material unit held by the gripper from a starting position to an ending position wherein the starting position comprises a horizontal starting position and a vertical starting position, and the ending position comprises a horizontal ending position and a vertical ending position; wherein the hoist is configured to move the gripper along the vertical axis to a position that is directly below the moveable stage, when the moveable stage is in the first position; and wherein the hoist is configured to move the gripper along the vertical axis to a position that is directly below the moveable stage, when the moveable stage is in the second position that is adjacent to a side of the OHT vehicle; wherein the moveable stage is further configured to move the material unit configured to be held by the gripper from the horizontal starting position to the horizontal ending position, and the hoist is configured to move the material unit from the vertical starting position to the vertical ending position; wherein the starting position is at the suspended shelf and the ending position is the first position.
 2. The method of claim 1, wherein the moveable stage is configured to move without rotating the gripper and the material unit.
 3. The method of claim 1, wherein the moveable stage is further configured to move the gripper along the horizontal axis to a third position on the opposite side of the OHT vehicle.
 4. The method of claim 1, wherein the hoist is configured to move the gripper from the first position vertically to a work station.
 5. The method of claim 4, wherein the workstation comprises a 300 mm load port.
 6. The method of claim 1, wherein the movable stage and the gripper are configured to work in concert to move the gripper to a storage location.
 7. The method of claim 1, wherein the material unit comprises a 300 mm front-opening unified pod.
 8. The method of claim 1, wherein the hoist is configured to move the gripper from the second position vertically to a storage location.
 9. The method of claim 8, wherein the storage location comprises the suspended shelf.
 10. The method of claim 1, wherein the moveable stage is configured to move without rotating the gripper and the material unit.
 11. The method of claim 1, wherein the moveable stage is further configured to move the gripper along the horizontal axis to a third position on the opposite side of the OHT vehicle.
 12. A method comprising: obtaining, by a gripper of an overhead transport (OTH) vehicle, a material unit from a suspended shelf; moving, by the overhead transport vehicle, the material unit held by the gripper from a starting position to an ending position wherein the starting position comprises a horizontal starting position and a vertical starting position, and the ending position comprises a horizontal ending position and a vertical ending position; wherein the overhead hoist transport (OHT) vehicle is coupled to an overhead rail in a semiconductor fabrication plant, and wherein the OHT vehicle comprises: the gripper configured to hold the material unit; a moveable stage coupled to the gripper, wherein the moveable stage is configured to move the gripper along a horizontal axis from a first position beneath the overhead rail to a second position adjacent to a side of the OHT vehicle; and a hoist coupled to the movable stage and to the gripper, wherein the hoist is configured to move the gripper along a vertical axis to a position that is directly below the moveable stage; wherein the hoist is configured to move the gripper along the vertical axis to a position that is directly below the moveable stage when the moveable stage is in the first position; wherein the hoist is configured to move the gripper along the vertical axis to a position that is directly below the moveable stage when the moveable stage is in the second position that is adjacent to the side of the OHT vehicle; wherein the moveable stage is further configured to move the material unit configured to be held by the gripper from the horizontal starting position to the horizontal ending position, and the hoist is configured to move the material unit from the vertical starting position to the vertical ending position; wherein the starting position is at the suspended shelf and the ending position is the first position.
 13. The method of claim 12, further comprising releasing the material unit at the ending position.
 14. The method of claim 12, wherein the starting position is at the OHT vehicle and the ending position is at a 300 mm process tool load port.
 15. The method of claim 14, further comprising releasing the material unit at the 300 mm process tool load port.
 16. The method of claim 12, wherein the second position is at a conveyer.
 17. The method of claim 12, wherein the starting position and the ending position are on opposite sides of the OHT vehicle.
 18. The method of claim 12, wherein moving the material unit comprises: moving the material unit from the starting position to the first position; moving to a new location along the track; and subsequent to reaching the new location, moving the material unit the ending position. 